It is a challenge to Hydro-form lightweight material such as aluminum or high strength steel in an effort to minimize the weight of the finished part. Hydro-formed parts may have areas of maximum strain that limit formability. If the maximum strength of a part is exceeded in a local area, the part may split. While strain may be maximized in certain localized areas, other areas of the hydro-formed part may have relatively low levels of strain. Corners and other highly formed areas are often located adjacent to areas where maximum strain is typically observed. Areas of maximum strain may also be adjacent to areas of lower levels of strain.
To avoid splitting in areas of high strain, more ductile materials having lower strength may be used. To provide the required strength, thicker tubes may be specified to provide the required strength. Thicker panels result in thicker parts and increase the weight of the final part. The use of thicker tubes also tends to increase material costs. Increased part weight reduces fuel economy. Hydro-formed parts may be formed in square, hexagonal or irregular shapes that include corners. If a part has corners, maximum strain may be predicted to be observed in narrow areas that are adjacent to the corners of the finished part.
Applicant has attempted to address the above challenges that tend to reduce the range of parts that may be made from lightweight material as summarized below.